export notmuch_database_reopen

[Reto]

Hi,
I'm trying to use the notmuch C library in a mail client.
Now, I learned that an open DB is essentially a snapshot at the time of opening.
If I want the current state of the notmuch DB, I need to reopen the DB.

The client I'm running is interactive and can have long running processes.
I'd like to avoid unnecessary create / destroy cycles of the DB,
especially as I'm calling the C lib via a go wrapper.

Would it be possible to export `_notmuch_database_reopen`?
Then I could call that instead. I mostly have a read only DB open anyhow.

Kind regards,
Reto